1. Field of the Invention
The present invention generally relates to memory storage devices of the type which includes at least one rotating disk as a memory storing means. More particularly, the present invention relates to rotating disk memory storage devices, normally called floppy disk drives, using a soft thin disk contained in a cover jacket for storing bits of information thereon.
2. Description of the Prior Art
In general, a floppy disk drive includes a driving hub and a pressure cone for securely holding a floppy disk therebetween, and the driving hub is driven to set the floppy disk in rotation. One typical prior art structure for holding a floppy disk for rotation, called "door bridge system", is schematically illustrated FIG. 11. As shown, this prior art structure includes a driving hub 70 which is operatively connected to a driving motor through a power transmission train (not shown) and drives a floppy disk 75 to rotate when it is securely held thereon. The floppy disk holding structure also includes a pressure cone 71 which is rotatably mounted on a door 73, which, in turn, is pivotally supported by a pin 72. In this structure, when the free end (left end in FIG. 11) is pushed downward to bring it to be in engagement with a latch 74 thereby setting the door 73 in a closed state, the cone 71 becomes pressed against the hub 70 so that the floppy disk 73 is securely held between the hub 70 and the cone 71. In such a structure, however, the door 73 has a relatively large mass, which thus requires a relatively large operating force for closing and opening the door 73. As a result, the floppy disk 75 may receive large shocks for mounting and dismounting and its overall operability is not entirely satisfactory. Furthermore, in order to cope with a large bending force imparted to the door 73, the door 73 must have a sufficient thickness especially at the portion above the floppy disk 75, and such a requirement is diametrically opposite to the recent trend of making a floppy disk drive as flat as possible.
Another typical prior art floppy disk holding structure is schematically illustrated in FIG. 12, and this structure includes a pressure cone 76 which is rotatably mounted on a leaf spring 77. Also provided is an actuating shaft 78 whose one end is off-centered and connected to the leaf spring 77 and the other end is connected to a pivotal door lever 79. In this structure, when the door lever 79 is pivoted in the direction as indicated by the arrow, the leaf spring 77 is caused to move downward through the shaft 78 thereby bringing the pressure cone 76 into pressure contact with a driving hub located therebelow. However, this structure also suffers from disadvantages of poor operability mainly due to the fact that an operator is required to pivot the door lever 79 for operation.
In addition, when it is desired to provide a driving motor in direct connection with the driving hub instead of employing a power transmission means such as a driving belt to apply a driving power to the driving hub from a motor located at a remote position, structural constraints in design become more severe because the overall device is generally required to be designed as flat as possible and movable parts such as the door 73 requires a larger stroke of movement for its enhanced operability, which apparently contradicts against the former requirement. Thus, there has also been a need to develop a new floppy disk drive which can satisfy these seemingly contradictory requirements as much as possible.